In general, a forklift truck is used for lifting up and unloading cargo, or transporting the cargo to a necessary location in a work place. The forklift truck is divided into an engine-type forklift truck and an electric-motor-type forklift truck according to a power source, and the engine-type forklift truck (hereinafter, abbreviated as the “forklift truck”) among them drives a hydraulic pump with an engine, drives a vehicle with pressured oil discharged from the hydraulic pump, and drives an operating device.
As illustrated in FIG. 1, a forklift truck 1 includes a mast 9 mounted to a vehicle frame 8 to be pivotable, a carrier 10 supported to the mast 9 in order to transport a cargo, a tilt cylinder 12 operating the mast 9 to be inclined based on a pivot point of the mast 9, a lift cylinder 11 operating the carrier 10 to be elevated, and the like.
The mast 9 is formed of an external mast 9a formed at an external side thereof and an internal mast 9b formed at an internal side thereof, and the internal mast 9b supports the carrier 10, and ascends/descends by the lift cylinder 11.
The tilt cylinder 12 and the lift cylinder 11 are operated by a tilt lever 13 and a lift lever 14, and the tilt lever 13 and the lift lever 14 are installed within a driver's cabin, so that a user may operate the tilt lever 13 and the lift lever 14 inside the driver's cabin.
In the meantime, in order to park the forklift truck 1, a parking brake 3 and a parking brake switch 21 for switching the parking brake 3 are formed on a front side of a driver's seat 2.
In general, a medium and large engine-type forklift truck identically uses battery power of about 24 direct current voltage (DCV), which is electric voltage specifications of all of the electric devices including a system power supply and an engine control unit (ECU).
However, the ECU in the present invention is operated at about 12 DCV, so that it is necessary to stably and continuously supply power of 12 DCV to the ECU.